1. Field of the Invention
This invention relates in general to running tools for running a casing hanger to a subsea wellhead housing and for setting a packoff between the casing hanger and the wellhead housing.
2. Description of the Prior Art
One type of subsea well completion utilizes a wellhead housing at the subsea floor. A string of casing will be lowered into the well once the well has been drilled to a certain depth. The casing hanger locates at the upper end of the string of casing and lands on a shoulder in the wellhead housing. Cement will be pumped down the string of casing to cement it in place. Then a packoff will be set between the casing hanger and the wellhead housing to seal the annulus.
There are a number of running tools for setting a packoff. Some use the weight of the casing string to set the packoff. Others use torque to set the packoff. Hydraulic pressure in the annulus is sometimes used to assist in setting the packoff.
In the past, most of the packoffs were metal or a combination of metal and elastomer. Now, metal-to-metal packoffs are used to avoid deterioration of the packoff over a long period of time. Metal-to-metal packoffs, however, require a much greater setting force than the prior elastomer packoffs. Consequently, running tools which will achieve the necessary force to set the packoff are desirable.